A cosmetic applicator includes: a seat that has a ventilation channel extending through an outer surface; an adjusting member that is disposed in a sleeve and that has several adjusting plates, an axial hole, and a gap formed in the adjusting plates and communicating the hole with the ventilation channel; and a core that extends through the hole, absorbs liquid cosmetic from a cartridge and defines a communicating channel with the adjusting member. The ventilation channel, the gap and the communicating channel define an air passage. The cartridge, the core and a bristle member define a liquid passage. Air is introduced into the cartridge through the air passage after the liquid cosmetic flows out of the cartridge through the liquid passage.